1. Field of the invention
The present invention relates to the production of alkylene carbonates. Alkylene carbonates are important materials as organic solvents, fabricating agents for synthetic fiber, raw materials for medicines or intermediates for dialkyl-carbonates.
2. Description of the Prior Art
Ethylene carbonate, one of the alkylene carbonates, is produced continuously by reacting ethylene oxide with carbon dioxide at about 240.degree. C. and 140 atmospheres using a pyridine catalyst as described in U.S. Pat. No. 2773881. However, because this industrial process of reacting ethylene oxide with carbon dioxide involves the reaction of explosive ethylene oxide at high pressure, there is a danger of explosion, and various counter-measures against explosion are required in this process.
Hitherto, various other processes for producing alkylene carbonates have been proposed. The process of reacting an alkylene glycol and urea to produce alkylene carbonate is remarkable, because both raw materials are relatively inexpensive and `alkylene carbonates` are easily produced therefrom. EP-A0443758 describes a process of reacting an alkylene glycol and urea at atmospheric pressure or higher either without catalyst or using a tin-containing catalyst. EP-A-0443758 shows an 84-99% selectivity of alkylene carbonate to reacted glycol, less than 66% conversion of glycol compared to theoretical conversion and less than 63% selectivity of alkylene carbonate to reacted urea. So a large part of the urea decomposes in this process.